The present invention relates to grass trimmers which use cutting lines. More specifically, the present invention relates to the configuration of the trimmer line and means of attachment of the trimmer line to the grass trimmer.
Standard trimmer line for a grass trimmer is wound around a spool within a trimmer head housing, such as illustrated in U.S. Pat. No. 5,623,765. The line is dispensed from the housing through one or more holes in the housing. A length of line extends from the housing and is spun by the trimmer at a high speed to cut grass or other vegetation. As the vegetation is trimmed, the line wears and shortens. Additional line is dispensed from the housing to restore the exposed line to the desired length for trimming. The mechanism for dispensing includes a spool within the housing which must rotate to unwind additional line and must then lock in placed to permit trimming. Because of the requirements of high speed rotation, spooling and dispensing, trimmers often have complicated head mechanisms. Accordingly, it is inconvenient and difficult to replace a coil of line on a trimmer head mechanism.
The structure of the spool and head mechanism has prevented the use of trimmer lines above a certain diameter. As the diameter of the trimmer line increase, it becomes stiffer and less flexible. The inflexibility of the line impedes its ability to be wrapped around a spool and hinders the ability to smoothly dispense the line from the spool during use. Therefore, a smaller diameter line will wrap and dispense more easily from a spool on a standard trimmer. Also a flexible, softer line will wind and dispense more easily from a coiled line trimmer than a stiffer harder line of the same diameter.
Unfortunately, the diameter and flexibility of the trimmer line directly impacts the wearing of the line. The smaller the diameter line, the faster the wear. The softer and more flexible the line, the faster the wear. A faster wear of the line is synonymous with a greater expense and inconvenience associated with the operation of a grass trimmer. The faster wear of the line results in more frequent need for replacement of the line and the spool, and eventual replacement of the head mechanism.
Several attempts have been made to provide a trimmer with a non-spooled trimming string, including U.S. Pat. No. 4,411,069 for a spooless string trimmer head to Close et al., U.S. Pat. No. 5,433,006 for a mowing apparatus to Taguchi, U.S. Pat. No. 5,406,708 for flexible rotating vegetation cutter to Stephens, U.S. Pat. No. 5,430,943 for a unitary cutting attachment for vegetation cutting devices to Lee, U.S. Pat. No. 5,303,476 for a line head for a rotary line trimmer to Tuggle, and U.S. Pat. No. 5,493,785 for a rotary grass cutting head to Lawrence.
It can also be desirable to use a trimmer line with a non-circular cross section, such as that illustrated in U.S. Pat. No. 5,463,815 for a ribbed flexible cutting line to Fogle. The use of a non-circular cross section can add strength and provide a sharper or cleaner cut of the grass. Unfortunately, such non-circular cross sections can also impede the dispensing of the line from a spool, especially if the line is of thick diameter. Accordingly, what is desirable is a non-circular cross section trimmer line which will overcome dispensing difficulties found in the prior art.